1. Field of the Invention
The present invention relates to light weight jacks for raising heavy objects, and more particularly, to jacks having plastic components to lessen the weight of such jacks as compared to conventional metallic jacks.
2. Description of the Prior Art
There are many types of jack mechanisms for raising heaving objects, particularly automobiles. Such jacks are a necessary part of the original equipment of automobiles, conveniently and compactly transported in the automobile to be on hand in case of an emergency requiring a jack, for example, a flat tire.
Such jacks are usually constructed of metal, which has the advantage of strength and durability. But there are also disadvantages to this material for the construction of jacks. Metal is a relatively expensive material because of the fabrication and process expense. Thus, the material greatly influences the cost of the jack. Metals, particularly relatively inexpensive metals, corrode. Corrosion effects the mechanics of the jack, such as interfering with relative movements between working parts. Metal parts coming into contact with one another clank and rattle. Consequently, a metal jack in the trunk of a car makes loud noises and sends vibration throughout its carrier. Metal also makes jacks heavy, adding to the overall weight of the automobiles in which they are transported. Additions to the weight of an automobile reduce its mileage efficiency. Moreover, heavy metal objects such as jacks stored in the trunk of an automobile become missiles under the right, or if you will, wrong conditions, such as sudden arrest of the automobile in a collision. The severity of the missile phenomenon is also related to the weight of the jack as a function of the momentum of the jack in a fast moving vehicle.
While it is known that weight reductions may be achieved by using low weight material, no successful jack device for heavy objects has been constructed of low weight plastic material because no structure has been developed to be made of plastic while being strong enough to lift a heavy object such as a motor vehicle. One drawback in adapting existing jack structures to plastic construction is that the standard metal jacks are better able to withstand the bending and torsion forces to which the jacks are exposed. Another drawback is that the base of a plastic jack lacks the weight of a metal jack so that it lacks the weight component necessary for frictional interface with the ground to keep the base from "kicking out." This particularly happens in the initial working of the jack to seat itself with a leverage that transfers the weight of the automobile to the base in a particular alignment.